M4 body thread problems

[chas]

So I bought this ACM M4 body for a Mk18 Mod 1 (DD RIS II) project: http://aegcartasia.com/mbaf37.html

 

Neither barrel nut that came with the (ACM) RIS nor the one that came with the KAC style RIS fit on the new body, but they do fit on the Dboys body that is the base gun. It's not that it doesnt fit, it just screws in halfway down the thread. Then it is so hard to turn further, that I don't want to force it an risk breaking either the thread on the body or on the barrel nut.

 

Anyone else encountered this problem? Could the thread on the upper body be out of spec or maybeimperial instad of metric?

 

Thanks in advance for any suggestions!

[aac]

 I encountered this problem to with my Mk18 project  i bought the Big Dragon M4 receiver, a complete disaster

Markings with "spelling mistakes", parts witch doesn't fit, without some thorough gunsmithing,

So how's that on your ACM receiver,  besides ?

 

I think only G&P has a another thread size, the rest should be equal ( i think ?)

Now as far as my experience with Airsoft thread in general goes, the standardisation is horrible !

 

Try to measure the Major Ø, and pitch from both the DBoys, and ACM , to compare them.

(if you dont have a thread pitch gauge, measure the distance between first and last crest , and divide it by the number of crest's)  

 

[chas]

Thanks. The receiver is quite nice. Markings are almost deep enough all over. No mistakes, as far as I can see.

 

What's weird is that it screws in half way, then why not all the way down?

[aac]

Can you post (or send me) some detailed close up photo's (of the markings)?

And how do the parts fit ?

 

how your general experience with that shop ?

 

When the nut screws just halfway this could mean A: the pitch is different. 

                                                                                        B: the thread is not wel made, variations in major diameter and/or thread depth. 

[mimesis]

There are three or four "standard" threads, and then tolerance differences between different manufacturers.  When the tolerances are slack, you can sometimes screw on a barrel nut that in theory shouldn't fit.  There was a lot of discussion about this years ago, here and on some of the US forums.

 

Madbull make this because of this exact problem: http://www.evike.com/products/28579/

 

If you can find the exact size, probably much cheaper to buy a generic equivalent off a tool website.

[chas]

I found a delta ring that fits. I just cut off the "crown" and spent hal of the evenening sanding it to size.

 

Just to find out, that the ring on the barrel (the protuberance that prevents the barrel from sliding further into the body) is to thick and Im slowly filing it down. Hope to be done in an hour or so.

[Beeingmyself]

Hehe welcome to airsoft gunsmithing.

There are so many things that is completly off spec.

Once sae at CA body and Madbull DD rail when mounted there was a difference in between the rail on more than af milimeter.

Looked awful.

 

The reason the barrelnut will only go half way down can be because the threads are just 1/100mm of each other.

Remember when milling in metal we are talking about 1/1000mm of a milimeter and the thread will not match

or be impossible the make a snug fit

 

I usuakky have the crown machined off the barrel nut due it is most likely to fit the reciever best.

[chas]

You definitely need specialized tools for gunsmithing:

 

I cut the crown of the barrel nut off with a radial arm saw. Then I had to sand it down and fine sand it to the specific size that would allow the DD rail to meet the receiver rail.

 

Then I decided to test fit it with the barrel on and the barrel ring is too thick, so I spend 2 hours filing that by hand.

 

A little more work today and Ill be done. What a pain in the *albatross*.

[chas]

Just a heads up: Do NOT buy this body. It's a piece of ######:

 

- I had to sand down the protubarance on the back of the Dboys gearbox so the bearbox would sit in the boddy correctly. Sill dont know if it will align with the hop up properly.

 

- The body pins need to be hammered in. Evenso, there is a small gap between upper and lower.

 

- The following parts need to be sanded down to fit: pin for the fake bolt release, fire selector, the fake fire selector on the right side.

 

- There's a small gap etween the pistol grip and the body.

 

- The ejection port door doesn't stay closed.

 

- The fake bolt doesn't move freely and has to be pushed to the front after opening.

 

It looks good (it has no fire selector markings on the right side), but it a pain in the *albatross*.

[DeltaZero]

You're having a good time with this body.. Can I ask, why didn't you just buy a G&P or other big brand receiver set that you know will work?

 

 

Sent from my iPhone using Tapatalk

[chas]

You're having a good time with this body.. Can I ask, why didn't you just buy a G&P or other big brand receiver set that you know will work?

 

 

Sent from my iPhone using Tapatalk

 

a) Im cheap.

 

 I wasnt aware that this was out of spec (even to its own components). Now that i know, I may buy G&P in the future.

[kingmaker]

Hi to make the barrel nut fit just get a triangular file(equalateral triangle cross section) and file in the grooves of the thread,.

It wont make a few minutes,it works and have done this myself